Discovery of soybean aphid biotypes

The soybean aphid [Aphis glycines Matsumura. (Hemiptera: Aphididae)] is an invasive insect pest of soybean [Glycine max (L) Merr.] that was first reported in North America in There are currently no reports of soybean aphid biotype diversity and this information is needed before aphid resistance genes are deployed. The objective of this research was to test for aphid biotype variation. The response of two A. glycines isolates, one collected in Ohio and the other in Illinois, were compared by infesting eight soybean genotypes in nonchoice tests. The same genotypes also were tested with the Ohio isolate using a choice test. In the nonchoice test, there was a significant (P < 0.0001) effect of aphid isolate, genotype, and a significant aphid isolate by soybean genotype interaction for the number of aphids per plant 10 and 15 d after infestation. The responses of the eight genotypes to the Ohio isolate in the choice test were similar to their responses in nonchoice tests. PI 200538 and PI 567597C were resistant to both the Ohio and Illinois isolates and will be useful sources of resistance to both isolates. These tests confirm that there are at least two distinct biotypes of A. glycines in North America.